qtmultimedia/src/multimedia/effects/qwavedecoder_p.cpp

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#include "qwavedecoder_p.h"

#include <QtCore/qtimer.h>
#include <QtCore/qendian.h>

QT_BEGIN_NAMESPACE

QWaveDecoder::QWaveDecoder(QIODevice *s, QObject *parent):
    QIODevice(parent),
    haveFormat(false),
    dataSize(0),
    source(s),
    state(QWaveDecoder::InitialState),
    junkToSkip(0),
    bigEndian(false)
{
    open(QIODevice::ReadOnly | QIODevice::Unbuffered);

    if (enoughDataAvailable())
        QTimer::singleShot(0, this, SLOT(handleData()));
    else
        connect(source, SIGNAL(readyRead()), SLOT(handleData()));
}

QWaveDecoder::~QWaveDecoder()
{
}

QAudioFormat QWaveDecoder::audioFormat() const
{
    return format;
}

int QWaveDecoder::duration() const
{
    return size() * 1000 / (format.sampleSize() / 8) / format.channels() / format.frequency();
}

qint64 QWaveDecoder::size() const
{
    return haveFormat ? dataSize : 0;
}

bool QWaveDecoder::isSequential() const
{
    return source->isSequential();
}

qint64 QWaveDecoder::bytesAvailable() const
{
    return haveFormat ? source->bytesAvailable() : 0;
}

qint64 QWaveDecoder::readData(char *data, qint64 maxlen)
{
    return haveFormat ? source->read(data, maxlen) : 0;
}

qint64 QWaveDecoder::writeData(const char *data, qint64 len)
{
    Q_UNUSED(data);
    Q_UNUSED(len);

    return -1;
}

void QWaveDecoder::handleData()
{
    // As a special "state", if we have junk to skip, we do
    if (junkToSkip > 0) {
        discardBytes(junkToSkip); // this also updates junkToSkip

        // If we couldn't skip all the junk, return
        if (junkToSkip > 0)
            return;
    }

    if (state == QWaveDecoder::InitialState) {
        if (source->bytesAvailable() < qint64(sizeof(RIFFHeader)))
            return;

        RIFFHeader riff;
        source->read(reinterpret_cast<char *>(&riff), sizeof(RIFFHeader));

        // RIFF = little endian RIFF, RIFX = big endian RIFF
        if (((qstrncmp(riff.descriptor.id, "RIFF", 4) != 0) && (qstrncmp(riff.descriptor.id, "RIFX", 4) != 0)) ||
            qstrncmp(riff.type, "WAVE", 4) != 0) {
            source->disconnect(SIGNAL(readyRead()), this, SLOT(handleData()));
            emit invalidFormat();

            return;
        } else {
            state = QWaveDecoder::WaitingForFormatState;
            if (qstrncmp(riff.descriptor.id, "RIFX", 4) == 0)
                bigEndian = true;
            else
                bigEndian = false;
        }
    }

    if (state == QWaveDecoder::WaitingForFormatState) {
        if (findChunk("fmt ")) {
            chunk descriptor;
            peekChunk(&descriptor);

            if (source->bytesAvailable() < qint64(descriptor.size + sizeof(chunk)))
                return;

            WAVEHeader wave;
            source->read(reinterpret_cast<char *>(&wave), sizeof(WAVEHeader));
            if (descriptor.size > sizeof(WAVEHeader))
                discardBytes(descriptor.size - sizeof(WAVEHeader));

            // Swizzle this
            if (bigEndian) {
                wave.audioFormat = qFromBigEndian<quint16>(wave.audioFormat);
            }

            if (wave.audioFormat != 0 && wave.audioFormat != 1) {
                // 32bit wave files have format == 0xFFFE (WAVE_FORMAT_EXTENSIBLE).
                // but don't support them at the moment.
                source->disconnect(SIGNAL(readyRead()), this, SLOT(handleData()));
                emit invalidFormat();

                return;
            } else {
                format.setCodec(QLatin1String("audio/pcm"));

                if (bigEndian) {
                    int bps = qFromBigEndian<quint16>(wave.bitsPerSample);

                    format.setSampleType(bps == 8 ? QAudioFormat::UnSignedInt : QAudioFormat::SignedInt);
                    format.setByteOrder(QAudioFormat::BigEndian);
                    format.setFrequency(qFromBigEndian<quint32>(wave.sampleRate));
                    format.setSampleSize(bps);
                    format.setChannels(qFromBigEndian<quint16>(wave.numChannels));
                } else {
                    int bps = qFromLittleEndian<quint16>(wave.bitsPerSample);

                    format.setSampleType(bps == 8 ? QAudioFormat::UnSignedInt : QAudioFormat::SignedInt);
                    format.setByteOrder(QAudioFormat::LittleEndian);
                    format.setFrequency(qFromLittleEndian<quint32>(wave.sampleRate));
                    format.setSampleSize(bps);
                    format.setChannels(qFromLittleEndian<quint16>(wave.numChannels));
                }

                state = QWaveDecoder::WaitingForDataState;
            }
        }
    }

    if (state == QWaveDecoder::WaitingForDataState) {
        if (findChunk("data")) {
            source->disconnect(SIGNAL(readyRead()), this, SLOT(handleData()));

            chunk descriptor;
            source->read(reinterpret_cast<char *>(&descriptor), sizeof(chunk));
            if (bigEndian)
                descriptor.size = qFromBigEndian<quint32>(descriptor.size);

            dataSize = descriptor.size;

            haveFormat = true;
            connect(source, SIGNAL(readyRead()), SIGNAL(readyRead()));
            emit formatKnown();

            return;
        }
    }

    if (source->atEnd()) {
        source->disconnect(SIGNAL(readyRead()), this, SLOT(handleData()));
        emit invalidFormat();

        return;
    }
}

bool QWaveDecoder::enoughDataAvailable()
{
    chunk descriptor;
    if (!peekChunk(&descriptor))
        return false;

    // This is only called for the RIFF/RIFX header, before bigEndian is set,
    // so we have to manually swizzle
    if (qstrncmp(descriptor.id, "RIFX", 4) == 0)
        descriptor.size = qFromBigEndian<quint32>(descriptor.size);

    if (source->bytesAvailable() < qint64(sizeof(chunk) + descriptor.size))
        return false;

    return true;
}

bool QWaveDecoder::findChunk(const char *chunkId)
{
    chunk descriptor;
    if (!peekChunk(&descriptor))
        return false;

    if (qstrncmp(descriptor.id, chunkId, 4) == 0)
        return true;

    // It's possible that bytes->available() is less than the chunk size
    // if it's corrupt.
    junkToSkip = qint64(sizeof(chunk) + descriptor.size);
    while (source->bytesAvailable() > 0) {
        // Skip the current amount
        if (junkToSkip > 0)
            discardBytes(junkToSkip);

        // If we still have stuff left, just exit and try again later
        // since we can't call peekChunk
        if (junkToSkip > 0)
            return false;

        if (!peekChunk(&descriptor))
            return false;

        if (qstrncmp(descriptor.id, chunkId, 4) == 0)
            return true;
    }

    return false;
}

// Handles endianness
bool QWaveDecoder::peekChunk(chunk *pChunk)
{
    if (source->bytesAvailable() < qint64(sizeof(chunk)))
        return false;

    source->peek(reinterpret_cast<char *>(pChunk), sizeof(chunk));
    if (bigEndian)
        pChunk->size = qFromBigEndian<quint32>(pChunk->size);

    return true;
}

void QWaveDecoder::discardBytes(qint64 numBytes)
{
    // Discards a number of bytes
    // If the iodevice doesn't have this many bytes in it,
    // remember how much more junk we have to skip.
    if (source->isSequential()) {
        QByteArray r = source->read(numBytes); // uggh, wasted memory
        if (r.size() < numBytes)
            junkToSkip = numBytes - r.size();
        else
            junkToSkip = 0;
    } else {
        quint64 origPos = source->pos();
        source->seek(source->pos() + numBytes);
        junkToSkip = origPos + numBytes - source->pos();
    }
}

QT_END_NAMESPACE

#include "moc_qwavedecoder_p.cpp"